1. Field of the Invention
The present invention relates to a process for preparing dicyan from prussic acid and oxygen according to the following formula: EQU 2HCN+ 1/2 O.sub.2 .fwdarw. (CN).sub.2 + H.sub.2 O
oxamide, oxalic acid and the like can be prepared by hydrolysis of dicyan. Besides dicyan is useful as a raw material for synthesizing nitrogen-containing compounds having various physiological activities and, therefore, an inexpensive synthetic process thereof is expected to be developed.
Prussic acid is most convenient as a raw material for dicyan, and, at the present time the supply of prussic acid on a large scale is possible by an increase of the production of acrylonitrile by ammoxidation of propylene, the development of an industrial process for preparing dicyan from prussic acid meets the above described expectations.
2. Description of the Prior Art
As a process for preparing dicyan from prussic acid, a method of dehydrogenating prussic acid, a method of using a nitrogen oxide as an oxidizing agent, a method of using chlorine as an oxidizing agent, and a method of partially oxidizing prussic acid with oxygen, and the like have hitherto been known. Among them, in the method of partial oxidation of prussic acid with oxygen, when silver (BP No. 932,520 ) or platinum-palladium alloy (U.S. Pat. No. 3,239,309 ) is used as a catalyst and oxygen is used in an amount of below stoichiometric amount necessary for oxidation of prussic acid to dicyan, the selectivity for dicyan is excellent as 70 to 90% although the conversion of prussic acid is low. However, the method of using those catalysts has such a defect that an elevated reaction temperature is required.
In addition there are methods of using a simple substance of gold (German Pat. No. 1,056,101 ) or silver (U.S. Pat. No. 2,712,493 ) or an oxide or hydroxide of lithium, magnesium, molybdenum, manganese, nickel or silver (U.S. Pat. No. 3,065,057 ), as a catalyst and using oxygen as an oxidizing agent, these methods are low in yield of dicyan since the reaction condition is severe and cyanic acid (HOCN) is produced as a byproduct.